IDR J. Heitz, Ed.
Internet-Draft Cisco
Intended status: Standards Track J. Snijders, Ed.
Expires: April 29, 2017 NTT
K. Patel
Arrcus
I. Bagdonas
Equinix
A. Simpson
Nokia
N. Hilliard
INEX
October 26, 2016
Large BGP Communitiesdraft-ietf-idr-large-community-05
Abstract
This document describes the Large BGP Communities attribute, an
extension to BGP-4. This attribute provides a mechanism to signal
opaque information within separate namespaces to aid in routing
management. The attribute is suitable for use in four-octet ASNs.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 29, 2017.
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Internet-Draft Large BGP Communities October 2016
Autonomous System Number (ASN) and the least significant word is a
locally defined value whose meaning is assigned by the operator of
the Autonomous System in the most significant word.
Since the adoption of four-octet ASNs [RFC6793], the BGP Communities
attribute can no longer accommodate the above encoding, as a two-
octet word cannot fit a four-octet ASN. The BGP Extended Communities
attribute [RFC4360] is also unsuitable, as the protocol limit of six
octets cannot accommodate both a four-octet Global Administrator
value and a four-octet Local Administrator value, which precludes the
common operational practice of encoding a target ASN in the Local
Administrator field.
To address these shortcomings, this document defines a Large BGP
Communities attribute encoded as one or more twelve-octet values,
each consisting of a four-octet ASN and two four-octet operator-
defined values, each of which can be used to denote properties or
actions significant to that ASN.
2. Large BGP Communities Attribute
This document creates the Large BGP Communities attribute as an
optional transitive path attribute of variable length. All routes
with the Large BGP Communities attribute belong to the community
specified in the attribute.
The attribute consists of one or more twelve-octet values. Each
twelve-octet Large BGP Communities value represents three four-octet
values, as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global Administrator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Data Part 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Data Part 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Global Administrator: A four-octet namespace identifier. This
SHOULD be an Autonomous System Number.
Local Data Part 1: A four-octet operator-defined value.
Local Data Part 2: A four-octet operator-defined value.
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The Global Administrator field is intended to allow different
Autonomous Systems to define Large BGP Communities without collision.
Implementations MUST allow the operator to specify any value for the
Global Administrator field.
There is no significance to the order in which Large BGP Communities
are encoded in the BGP path attribute payload. A BGP speaker can
transmit them in any order.
Duplicate Large BGP Communities SHOULD NOT be transmitted. A
receiving speaker SHOULD silently remove duplicate Large BGP
Communities from a BGP UPDATE message.
3. Aggregation
If a range of routes is aggregated, then the resulting aggregate
should have a Large BGP Communities attribute which contains all of
the Large BGP Communities attributes from all of the aggregated
routes.
4. Canonical Representation
Large BGP Communities MUST be represented as three separate unsigned
integers in decimal notation, without leading zeros, in the following
order: Global Administrator, Local Data 1, Local Data 2. Numbers
MUST not be omitted, even when zero. For example: 64496:4294967295:2
or 64496:0:0 or (64496, 111, 222).
5. Reserved Large BGP Community values
The following Global Administrator values are reserved: 0 (the first
ASN) [RFC7607], 65535 (UINT16_MAX) and 4294967295 (the last ASN)
[RFC7300]. Operators SHOULD NOT use these Global Administrator
values.
Although this document does not define any Special-Use Large BGP
Communities, the Global Administrator values specified above could be
used if there is a future need for them.
6. Error Handling
The error handling of Large BGP Communities is as follows:
o A Large BGP Communities attribute SHALL be considered malformed if
its length is not a non-zero multiple of 12.
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o A BGP UPDATE message with a malformed Large BGP Communities
attribute SHALL be handled using the approach of "treat-as-
withdraw" as described in section 2 [RFC7606].
The Large BGP Communities Global Administrator field may contain any
value, and a Large BGP Communities attribute MUST NOT be considered
malformed if the Global Administrator field contains an unallocated,
unassigned or reserved ASN or is set to one of the reserved Large BGP
Community values defined in Section 5.
7. Security Considerations
This extension to BGP has similar security implications as BGP
Communities [RFC1997].
This document does not change any underlying security issues
associated with any other BGP Communities mechanism. Specifically,
an AS relying on the Large BGP Communities attribute carried in BGP
must have trust in every other AS in the path, as any intermediate
Autonomous System in the path may have added, deleted or altered the
Large BGP Communities attribute. Specifying the mechanism to provide
such trust is beyond the scope of this document.
Network administrators should note the recommendations in Section 11
of BGP Operations and Security [RFC7454].
8. Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
As of today these vendors have produced an implementation of Large
BGP Communities:
o Cisco IOS XR
o ExaBGP
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